The invention relates to the manufacture and composition of a structural panel of a form normally used in the construction of residential and commercial buildings.
Reference is made to United States Patent Office Disclosure document 214688, dated Nov. 21, 1988, pursuant to which the inventor recorded with the United States Patent Office, proof of his conception of the idea on or before that date receipt of which has not yet been acknowledged.
Structural panel is frequently used to form the interior walls of residential and commercial structures. Structural panel typically comprises a hardened plaster or cement mixture sandwiched between a screen, scrim, or stabilizing material. Normally some sheet of a smooth material is pasted against one side of the structural panel to give it at least one smooth surface. Structural panel is typically cut to industrially standardized sizes so that its use can be readily planned and the requisite numbers of structural panel sheets can be ordered for use in construction.
One advantage of the use of structural panel is that it is easy to work with. While providing many of the rigidity qualities of concrete, due to its use of cement for substance, the fact that typical structural panel sheets are less than an inch in thickness permits a rather large sheet to be handled by one or two persons. Another advantage of structural panel is that it can easily be cut to appropriate sizes and adjacent sizes of structural panel can be "smoothed together" by a mud solution which is taped over and sanded flush with the surrounding wall. Numerous forms of structural panel are in use, but it is always advanatageous to find a material which satisfies all the requirements of structural panel and is yet lighter, stronger, and easier to work with.
Gypsum plaster is one form of plaster which has experienced widespread use in the manufacture of structural panel. A distinct advantage of the use of gypsum plaster is that it is easy to mold and shape, but its disadvantages are that it is heavy and somewhat brittle. Accordingly, ways of modifying standard guysum plaster have been frequently sought.
One consistent problem with structural panels is the contraction and expansion effects of temperature upon them. Such panels are normally posistioned as closely together as possible in order to provide a smooth wall surface. As described avove, the crack between them is filled with a plaster or mud compound and, upon drying, is sanded or otherwise made flush with the panel surfaces. If the effects of temperature cause the panels to expand or contract however, these joints will be compromised by buckling with expansion or opening cracks during contraction.
Vermiculite is a packing material which is commonly found in particle sizes of approximate equivalents to a person's fingernail. The reason it is useful as a packing material is that it has good insulation qualities, does not deteriorate under the influence of moisture or humidity, and has the quality of providing cushioning. Vermiculite can best be described as a fibrous plastic material with air pockets within its surface. The insulation, durability, and temperature behavior qualities of vermiculite would be appropriate for structural panel. Structural panel however, by its nature and in line with its intended uses, must be a rigid material. The present art does not provide a form of structural panel which adequately makes use of vermiculite.